1. Technical Field
The present invention relates to an undersea vehicle for research applications and components thereof
2. Related Background Art
Access to the seabed has been by possible for centuries using ropes of various compositions, chains, and as of the middle of the 20th Century, by free vehicles. Free vehicles are chambers that can contain observational or sampling equipment that operate autonomously within the ocean depths. Free vehicles operate independently of the surface or ships by the sequential control of buoyancy. In the simplest configuration, a positive buoyancy module, also called “flotation,” is overcome by a larger negative weight, also called an “anchor,” making the vehicle's net density greater than seawater, and therefore able to sink to the sea floor. After a period of time, which can vary from a few seconds to multiple years, the anchor is released from the flotation, making the upper package less dense than seawater. It now floats to the surface, generally carrying with it physical samples, recorded data, or both.
Heretofore the free vehicles have been custom made for a specific mission or task. Some vehicles are made for a particular observation and others are constructed for particular sampling tasks, including collecting water at varying depths or biological and geological samples from the ocean floor. There are no general-purpose free vehicle platforms that can be adapted to a variety of purposes.
Prior art free vehicle platforms are attached to an anchor that drags them to the ocean floor. Once below the surface communication with the free vehicle becomes a challenge. The water is opaque to radio waves so communication must be through wires or acoustically. The extreme ocean depths frequently explored make sending commands to the free vehicle impossible. The free vehicle must be able to operate autonomously. The autonomous operation must include determining when the vehicle will release from the anchor and return to the ocean surface for recovery. Prior art release has included anchor connections that corrode at a known rate such that the free vehicle will literally break free from the anchor after a pre-selected time. The rate of corrosion however is rarely consistent. Local water chemistry, temperature and currents affect the corrosion rate such that the time of release of the free vehicle can vary significantly. Electronic timers can be used to trigger release events however release mechanisms that operate consistently at extreme ocean depths are heretofore not available. Autonomous operation must further include reliable mechanisms to shutdown electronic devices once the vehicle is submerged and to restart the devices once it resurfaces. Electronic devices must be shut down to conserve battery life for what can be submerged missions that last for days.
Locating a free vehicle once the measurements or sampling is completed is also difficult. With currents potentially moving the free vehicle some distance from the drop point, or a dark night, overcast or storms, it may be difficult to locate the small but expensive floating device as it sits low in the water. Further, biological samples carried from the depths may be sterilized by the warm surface waters in a matter of 30 minutes or less. Ship costs can run over $40,000/day, and any delay can be expensive. Thus, it is crucial to locate and recover the device in the shortest period of time. Finding the device is critical to a mission's success. Use of a radio direction finder homing beacon allows skilled operators using null meters to determine the approximate direction, but not range. Skill is required as the indicated direction may be out by 180-degrees, and the ship could head directly away from the free vehicle. There are two prior art beacons that utilize global positioning satellites and satellite communication to transmit a floating beacons location. Buoys and free vehicles using the Argos® systems (Argos is a registered trademark of Collecte Localisation Satellites C.L.S. société anonyme (sa) of France) sends the received position to a computer email address, therefore requiring a satellite link to the Internet to access the required information. Such links are often not accessible at sea. MetOcean Data Systems of Canada forwards the positional information from a drifting surface buoy via a satellite telephone to a land-based service that then relays the coordinates back to the ship through a satellite telephone, a loop process that can have significant delay and result in difficulty in locating a free vehicle drifting in ocean currents. The current methods are slow, costly, and less capable as they only provide the location of the floating device, but not a bearing and range relative to the ship. Additionally, navigational charts must be employed to find the broadcasting devices location relative to the recovery ship.
There is a need for a vehicle platform that can be adapted to a variety of uses. There is a need for a free vehicle that uses a standard set of parts and procedures for traversing ocean depths and returning and still provides a cargo bay for custom experiments. There is a need for a free vehicle system that is expandable to handle a variety of experiments and allows for communication amongst all experiments simultaneously immersed. There is a need for a free vehicle platform that can operate autonomously at ocean depths. There is a need for a free vehicle platform that can be precisely released from an anchor so that it may be quickly and efficiently recovered. There is a need for a platform that can be located at sea by broadcasting its location and heading to a recovery vessel over long distances. The free vehicle requires a combination of capabilities to perform. There must be mechanisms in place for autonomous operation including shutdown and startup procedures for portions of the onboard electronics as the vehicle is submersed, there must be reliable attachment and release mechanisms for the anchor, and there must be robust position and communication systems to retrieve the free vehicle when it resurfaces. Additionally for cost and reliable operation there is a need for a free vehicle that isolates the navigation features of the vehicle from the cargo experiment features of the vehicle, such that navigation can be done repeatedly and reliably while the onboard experiments may be customized for each trip to the ocean floor.